This invention relates generally to pressure seals and, more particularly, to seal arrangements in a piping system for pressurized gas or vacuum pumping which permits rotary motion of the vessel being filled or evacuated.
In the manufacturing of lamps, it is desirable in many applications to have the lamp envelope rotating at high speeds while at the same time filling the lamp with pressurized gas or pumping gas from the lamp to create a vacuum therein. For example, the lamp envelope may be mounted on a rotating lathe over a glass-sealing fire, and uniform glass necking and sealing operations may be performed while at the same time pumping and flushing the interior of the lamp. In order to obtain such an arrangement, a rotary seal that is stationary at one end and free to rotate at the other end is required. Such a seal must be vacuum and pressure tight when rotating.
Previously available rotary seal devices have been relatively complicated and expensive. For example, such devices have involved the use of a plurality of graphite O-rings on a polished, hardened steel shaft having an apertured bore therethrough and rotatably mounted within a steel cylinder. The outer cylinder included a plurality of inlet and outlet bores and additional bores associated with an axilliary vacuum pumping system to assure a gas-tight vacuum seal about the O-rings.